fix(release): fail closed on malformed WebUI metadata

tools/release/govoplan_release/selective_planner.py

@@ -154,10 +154,34 @@ def apply_release_webui_bundle_gate(
     workspace: Path,
 ) -> tuple[ReleasePlanUnit, ...]:
     issues_by_repo: dict[str, list[ReleaseGateFinding]] = {}
-    for issue in selected_release_webui_bundle_issues(
-        repo_versions={unit.repo: unit.target_version for unit in units},
-        workspace=workspace,
-    ):
+    try:
+        issues = selected_release_webui_bundle_issues(
+            repo_versions={unit.repo: unit.target_version for unit in units},
+            workspace=workspace,
+        )
+    except Exception as exc:  # noqa: BLE001 - source errors become release findings.
+        for unit in units:
+            issues_by_repo.setdefault(unit.repo, []).append(
+                ReleaseGateFinding(
+                    code="release_webui_metadata_unreadable",
+                    severity="blocker",
+                    message=(
+                        "Release WebUI composition metadata could not be read or parsed "
+                        f"({type(exc).__name__})."
+                    ),
+                    remediation=(
+                        "Repair malformed JSON in the selected module WebUI package or "
+                        "Core's release package/lockfile, refresh the repository "
+                        "dashboard, then rebuild this plan."
+                    ),
+                    repo=unit.repo,
+                    source="release WebUI composition metadata",
+                    expected=unit.target_version,
+                    actual="unreadable",
+                )
+            )
+        issues = ()
+    for issue in issues:
         issues_by_repo.setdefault(issue.repo, []).append(
             ReleaseGateFinding(
                 code="release_webui_composition_alignment",